Morphogenesis of immature female inflorescences of date palm in vitro

- Morphogenesis of immature female inflorescences of date palm in vitro.
- a The Central Laboratory of Date Palm Researches and Development, Agriculture Research Center, Cairo, Egypt.
- Female inflorescences;.
- Abstract Plant regeneration from immature female inflorescences of date palm (Phoenix dactylifera L.) cultivar Siwi (semi-dry cv.
- Immature inflo- rescences explants were cultured on Murashige and Skoog (MS) medium supplemented with TDZ at 1.0 mg/l.
- The date palm (Phoenix dactylifera) is a perennial dioecious.
- ‘tree’ of the Arecaceae family, and has a great value particu- larly in North Africa and the arid regions of the Middle East by its economic importance and environmental impact (Kriaa et al., 2012).
- For some years the vegetative propagation of date palm by in vitro culture has been the subject of numerous studies using techniques such as somatic embryogenesis and organogenesis (Sharma et al., 1986.
- Bouguedoura et al., 1990.
- El Hadrami et al., 1995).
- Use of inflorescences as starting material has been rarely described by Drira and.
- These tissues are considering alternative source of tissues derived from offshoots without the risk of a definitive loss, particularly of the head clone genotypes limited only to one plant.
- Zayed (2011) tested many female inflorescences in different stages of development as explants and cultured on different concentrations of plant growth regulators.
- The results indicated that the most responsive starting material for initia- tion embryogenic cultures was the immature female inflores- cence with TDZ.
- Plant growth regulators have a major influence on tissue culture success as they are involved in the regulation of cell division, tissue and organ differentiation (Jennifer et al., 2010).
- However there is no consistent result published for discussing the relationship between the levels of endogenous plant hormones and reversion of the floral state of date palm cv.
- So that, this study aimed to make a correlation between hormonal, biochemical and morphogenesis changes via somatic embryogenesis and to better understand physiological and histological states of the explant (female inflorescences and its development to somatic embryogenesis)..
- 2014 at the Central Laboratory of Date Palm Researches and Development, Agricultural Research Center (ARC), Giza, Egypt, and Agricultural Botany Department, Faculty of Agriculture, Ain Shams University.
- This investigation was conducted to study the physiological and histological charac- ters which concerning with each stage via somatic embryogen- esis of immature female inflorescences of P.
- Immature female inflorescences of date palm (P.
- Sterilized inflorescence explant was divided longitu- dinally into 2–3 equal segments (spikes with part of inflores- cence base) for use as explants as described by Zayed (2011)..
- The explants were cultured horizontally with a good contact with the sur- face of the best basal inductive culture medium used in our present study which was chosen from previous studies made by Zayed (2011).
- Four samples were taken at different morphogenesis stages (immature female inflorescences, callus, embryogenic callus and mature somatic embryos) of date palm cv.
- Plant samples were harvested for histological study at different morphogenesis stages (immature female inflorescences, callus, embryogenic callus and mature somatic embryos) of date palm cv.
- The schedule of the paraffin method as described by Johansen (1940) was followed.
- Concerning different morphogenesis stages (Table 1), the high- est value of endogenous gibberellic acid (GA 3 ) was recorded by female inflorescences explant (18.88 mg/100 g FW) followed by callus, embryogenic callus and mature somatic embryo respec- tively and 0.113 mg/100 g FW)..
- Regarding endogenous auxin (IAA), data clearly revealed that the highest value of endogenous auxin (896.9 lg/100 g FW) was observed with female inflorescences explant while the mature somatic embryo produced the lowest value (8.2 lg/100 g FW).
- In developmental stages, a gradual increase in endogenous zeatin was noticed from immature female inflorescence to the.
- embryogenic callus stages lg/100 g FW).
- As for endogenous ABA (Abscisic Acid), endogenous ABA in immature female inflorescence and embryogenic callus was found with large amounts (30.79 and 50.01 lg/100 g FW) when compared to other developmental stages (callus and mature somatic embryos.
- The embryo- genic callus produced the highest value of endogenous ABA when compared with the immature female inflorescence..
- Immature inflorescence female stage led to significant increase in total soluble sugars and fractions (reducing and non-reducing sug- ars) as compared to the other developmental stages.
- It could be Table 1 The levels of endogenous hormones in the immature female inflorescence and its subsequent developmental stages of date palm cv.
- Inflore.
- Embryogenic callus .
- Immature female inflorescences..
- Table 2 The levels of total sugars, reducing sugars and non-reducing sugars in the immature female inflorescence and its subsequent developmental stages of date palm cv.
- Table 3 The levels of free amino acids, indoles and phenols in the immature female inflorescence and its subsequent developmental stages of date palm cv.
- noticed from Table 3 that the embryogenic callus and immature female inflorescence stages showed a significant increase in free amino acids concentration comparing with the other develop- mental stages (Callus and mature somatic embryos stages)..
- On the other hand, the other developmental stages (immature female inflo- rescence and mature somatic embryos) showed reduction in this concern..
- Structure of the immature female inflorescence.
- Morphology of the immature female inflorescence shows that the flower primordia and their subtending bracts firstly appear at the base of rachillae and are initiated solitary in an acropetal sequence as the rachillae elongate (Fig.
- At the end of the fifth week most of the pistillate flowers with their growing callus masses have been separated from the inflorescence axis and fall on the media (Fig.
- The friable portion of the callus was composed of disor- ganized masses of highly vacuolated cells ranging in diameter from 30 to 60 lm.
- All of the embryonic phases could be observed in these aggregations from a single cell, 2 celled, 4 celled, globular to bipolar structures (Fig.
- stage ‘‘the mature somatic embryo’’ could be achieved at the end of 4th to 6th week of the second subculture (Fig.
- Differences between immature female inflorescence and subse- quent developmental stages in endogenous hormone concen- trations and exogenous TDZ could explain these different morphogenetic responses.
- The findings presented in the cur- rent study revealed that the immature female inflorescence contained the highest level of GA 3 .
- This result matched well with Liu et al.
- This increase in gibberellins appeared to play an important role in inflores- cence development.
- Also, they reported that ABA increased in the same stage to maintain a certain balance between the inhibitor level and GA-like substances for controlling the growth rate of inflorescence and floral parts.
- Data presented here showed that, endogenous IAA reaches to its highest level in immature female inflorescences followed by embryogenic callus and then decreased reaching to its low- est level in mature somatic embryos.
- Requirement of auxin or other plant growth regulators for the initiation of somatic embryogenesis is largely determined by the developmental stage of the explant tissue (Kutscheram, 1994).
- These results are in harmony with Zein El Din (2010) who found that embryogenic callus of date palm contained much higher levels of endogenous ABA and declined in the individual somatic embryo.
- Manipulation of endogenous and/or exogenous ABA levels increases the fre- quency of embryos reaching maturity and can assist the han- dling of the large populations of somatic embryos which can be required for mass propagation (Ammirato, 1988)..
- The present data showed that endogenous zeatin concentra- tion was at its lowest level in the explant ‘‘immature inflores- cence’’ then, increased at the subsequent developmental.
- 1 Morphology and anatomy of immature female inflorescence of date plam cv.
- (a) Morphology of floral buds on rachilla of immature female inflorescence.
- (b) Longitudinal section of rachilla showing the meristematic state of the floral bud subtending with small bract.
- (d) Two to three weeks after culturing on media supplemented with TDZ showing development of callus all over the floral buds with increasing in flower size.
- (e) Longitudinal section in the same stage illustrating the initiation of callus from the epidermal and subepidermal layers of the floral buds, and the arrows indicate small callus masses arise from the floral bud.
- (g) One floral bud separated from the inflorescence axis with numerous callus masses at the end of 4–5 weeks of culturing.
- a, inflorescence axis.
- of cell division and metabolism of plant (Casanova et al., 2004;.
- Zhang et al., 2005).
- (a) Differentiation of date palm embryogenic callus from female floral bud 6 weeks after culture on medium free of cytokinin.
- Note the nodular appearance of the callus.
- (f) Longitudinal section in the bipolar embryo, note the polarity structure which consists of a meristematic end ‘‘the root tip (r.
- with a procambium (pr) strand and a more vacuolated tip ‘‘the cotyledon (c.
- Hutchinson et al., 1996.
- Murthy et al., 1998)..
- The present results showed that immature female inflores- cences contained much high levels of total sugars, reducing and non-reducing sugars, while callus contains the lowest level among the other developmental stages then, the level of total sugars, reducing and non-reducing sugars increase in the embryogenic callus.
- This increase of total sugars could also have occurred as a consequence of the uptake and meta- bolism of the carbohydrates supplied exogenously.
- Results of the present study reported that level of free amino acids, indoles and phenols in embryogenic callus is increased.
- The accumulation of amino acids during somatic embryogenesis was also reported for alfalfa, anise, and cowpea (Ramakrishnan et al., 2005)..
- et al., 1998).
- Fry (1986) observed that important role of pheno- lic acids is their involvement in the modulation of the cell wall composition.
- The key of the technique presented in the current study, which is based on completely undifferentiated female inflorescence, is the attainment of the callus.
- In fact, reversion of the floral meristematic cells into vegetative cells is a complicated process that requires a high control of various physicochemical and hormonal factors.
- This result is in line with that previously reported (Capelle et al., 1983;.
- Hutchinson et al., 1996).
- Indeed, the histological observations of date palm tissues showed the continuous effect of TDZ as a cytokinin not only in reaching the embryogenic callus but also in promoting suc- cessive divisions which led to the polarity of the proembryos..
- With respect to the explant (immature female inflores- cence), the flower primordia are constituted of meristematic cells.
- Several stud- ies have also reported that the differentiation degree of the date palm flowers is an important factor defining their ability to develop (Drira and Benbadis, 1985.
- Kriaa et al., 2012)..
- The possible use of immature female inflorescences is there- fore an attractive alternative since a single tree can produce many inflorescences per year that can be used as explants and offer several highly valued advantages, namely the possi- bility of reversion from the reproductive to the vegetative state..
- This deviation in morphogenetic behavior may be attributed to the age of inflorescences and/or the exogenous plant growth regulators.
- As compared to the vegetative tissue conferred to the floral tissues which characterizing with morphogenetic plasticity stands in contrast with the morphogenetic rigidity characterizing vegetative tissues in regeneration processes of date palm (Drira and Benbadis, 1985).
- Histological changes on regeneration in vitro culture of date palm (Phoenix dactylifera) leaf explants.
- Somatic embryogenesis from shoot tip and immature inflorescence of Phoenix dactylifera L.
- Vegetative multiplication of date palm (Phoenix dactylifera L.) by reversion of in vitro cultured female flower buds.
- Rapid micropropagation of date palm using floral tissues.
- Effects of Picloram in Inflorescence Culture of Oil Palm.
- The date palm (Phoenix dactylifera L.) micropropagation using completely mature female flowers.
- The current status of the acid-growth hypoth- esis.
- Vegetative multiplication of date palms from in vitro cultured inflorescences: effect of some growth.
- Histocytological analysis of callogenesis and somatic embryogenesis from cell suspensions of Date Palm (Phoenix dactylifera).
- Regeneration of plantlets from somatic tissues of the date palm (Phoenix dacylifera L).
- Field performance of tissue cultured date palm (Phoenix dactylifera) clonally produced by somatic embryogenesis.
- Physiological and Biotechnological Studies on Date Palm Micropropagation

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